# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 600, 400 
# set output 'surface1.1.png'
set grid nopolar
set grid xtics nomxtics ytics nomytics noztics nomztics nortics nomrtics \
 nox2tics nomx2tics noy2tics nomy2tics nocbtics nomcbtics
set grid layerdefault   lt 0 linecolor 0 linewidth 0.500,  lt 0 linecolor 0 linewidth 0.500
set hidden3d back offset 1 trianglepattern 3 undefined 1 altdiagonal bentover
set style data lines
set title "3D surface from a grid (matrix) of Z values" 
set xrange [ -0.500000 : 4.50000 ] noreverse
set yrange [ -0.500000 : 4.50000 ] noreverse
NO_ANIMATION = 1
## Last datafile plotted: "$grid"
splot '$grid' matrix with lines notitle